(Field of the Invention)
The present invention relates to a method and apparatus for controlling a reverse-conducting GTO device in which a gate turn-off (GTO) thyristor and a diode of opposite polarities formed on a single semiconductor substrate are connected in parallel.
In AC-DC, DC-AC, DC-DC or AC-AC/power converters which use a number of thyristors or gate turn-off thyristors, a freewheeling diode is often connected to each thyristor in an inverse parallel relationship.
It is therefore known, when using a thyristor to form an inverse-parallel unit of a thyristor and diode integrally on a single semiconductor substrate, to reduce the size of the entire device. For example, a semiconductor device in which a thyristor and diode are formed integrally is disclosed in the Proceedings of the 2nd Conference on Solid State Devices, Tokyo, 1970, Supplement to the Journal of the Japan Society of Applied Physics, Vol. 40, 1971. It is also practicable to form a reverse-conducting GTO thyristor when using a GTO thyristor and diode.
However, such a reverse-conducting GTO thyristor has the problem that, while the diode portion thereof recovers its ability to block reverse voltage, the GTO thyristor could undergo erroneous breakover, and this could destroy its emitter.